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The biosorption of methylene blue (MB) from aqueous solution by leaf residues of Thymus numidicus (RTN), Origanum glandulosum (ROG) and Sapindus mukorossi pericarp fibre (SMPF) was investigated in batch experiments. The effects of contact time, initial MB concentration, pH and biomass dosage on the biosorption capacity were investigated. Moreover, kinetic and equilibrium models were used to fit the experimental data. Equilibrium data were analysed using the Freundlich and Langmuir isotherms. Results show that the adsorption capacity increases until equilibrium is reached after 10 min of contact time. Furthermore, the amount of MB adsorbed per gram of biosorbent increases with pH in the pH range 2–5 but tends to decrease with pH in the pH range 7–10. Under optimal conditions, equilibrium sorption data are accurately represented by a pseudo-second-order kinetic model. The results show that the Langmuir model best describes the adsorption of methylene blue on the three biosorbents. At neutral pH and ambient temperature, the maximum adsorption capacities reached are 24.2, 33.3 and 41 mg of MB per gram of biosorbent, respectively, for SMPF, ROG and RTN. Thermodynamic studies showed that adsorption was spontaneous and endothermic with residues of ROG and SMPF but exothermic with RTN. Our results clearly reveal that RTN, ROG and SMPF act as effective adsorbents for the removal of methylene blue from aqueous solutions.

The sorption of divalent copper and nickel ions from aqueous solutions on natural and synthetic hydroxyapatites was investigated in batch mode at 25 and 40°C and over metal concentration range of 20–800 mg/L. Effect of initial pH solution was also investigated for two values pH 4.5 and pH 6. The sorption equilibrium data were well fitted by Langmuir’s model. Both hydroxyapatites are efficient to remove copper and nickel ions, despite their different compositions and morphologies. The sorption mechanism involved an ion exchange between calcium ions of hydroxyapatite and metal ions along with pronounced precipitation, particularly in case of the synthetic hydroxyapatite. Higher sorption efficiencies were observed with the synthetic hydroxyapatite towards copper ions, similar values for both synthetic and natural hydroxyapatites were found towards Ni ion’s sorption and lower values at pH 6.

The sorption of divalent cadmium and copper ions from aqueous solutions on natural and synthetic hydroxyapatite was investigated by the batch method and under dynamic conditions in columns at 22 °C and pH 5. The effect of cadmium and copper concentration on sorption was studied. Both types of apatites are efficient, despite their different composition and morphology. The sorption mechanism involves an ion exchange for Cd(II), while Cu(II) leads to precipitation of a newly formed solid. Thus, the sorption efficiency depends on the experimental conditions and the specific physicochemical properties of the apatites used. The sorption isotherms were fitted to the Langmuir equation.

Des méthodes relativement récentes, comme l’échange d’ions et l’extraction liquide-liquide, ont été largement utilisées pour séparer des métaux à l’état de traces. Pour ceux qui présentent notamment des propriétés analogues, la complexation par des agents chélatants s’avère nécessaire. Du fait de leur grande stabilité thermique et de la diversité des groupements fonctionnels des produits commerciaux disponibles, les résines ont été d’une grande utilité en analyse et dans l’industrie. Cette étude a trait à la rétention de métaux comme le cadmium et le zinc sur les résines acides Amberlite IRC-50, Dowex-50 X8 et Permutit C‑67. Les études en flacon ont mis en évidence une grande affinité de ces éléments pour les résines utilisées, et que l’équilibre est atteint rapidement (30 à 60 min). Les ions Zn2+ et Cd2+ n’utilisaient au maximum que 88 à 91 % de capacité totale des résines étudiées. Le traitement des résultats pour les faibles concentrations a montré que les isothermes sont du type Langmuir comme ceux obtenus par ailleurs sur des échangeurs minéraux.